Sighting mechanism



Nov. 11, 1958 c. s. GRlMsHAw 2,859,526

Y SIGHTING MEcHANrsu Filed Jan. 11, 1943 3 Sheets-Sheet 1 Irwvehtov: Charles B Grmshaw,

is Attorney.

Nov. 11, 1958 c. s. GRlMsHAw 2,859,526

v SIGHTING MECHANISM i Filed Jan. l1, 19?.5 3 Sheets-Sheet 2 Inventor-z 'Char les 5. Grimshaw,

5 Nov. 11, 1958 c. sfGRlMsHAw 2,859,526

SIGHTING MECHANISM Filed Jan. l1, 1943 3 Sheets-Sheet 3 Inventor-z Char-les 5. Gvmshaw, I

United States Patent SIGHTNG MECHANISM Charles S. Grimshaw, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application January 11, 1943, Serial No. 473,943

12 Claims. (Cl. S31- 49) This invention relates to sighting mechanism, more particularly to sighting mechanism for use in the control of gunre, and it has for its object the provision of improved `mechanism of this character.

While it has more general application, this invention is especially useful in the control of machine guns mounted on rapidly moving supports, such as aircraft, and directed at rapidly moving targets, as aircraft. And in general it relates to the type of sighting mechanism described and claimed in the copending application of F. V. Johnson, Serial No. 459,780, led September 26, 1942, now Patent No. 2,467,831 and assigned to the same assignee as the present invention.

The sighting mechanism of the Johnson application controls the line of re of the gun so as to give the 'gun the correct lead angle With relation to the line of sight to the target as required by the speed of the target. This is accomplished by a sight which is arranged to establish a line of sight to the target; the sight is mounted on a support which is movable so that the line of sight may be brought to bear on the target and track it; and the support as it is so moved, moves ina rigid system with the gun. Y

Also mounted on the support is a gyroscope which is free to move about a predetermined point of suspension andwhich is connected to the sight to control the line of sight with reference to the support and to the gun moved with the support; the gyroscope is coupled to the support, so that while the gyroscope may move relatively to the 'support to control the line of sight with reference to the gun, the coupling means exerts a torque onthe gyroscope which tends to `precess it to cause it lto follow the sight as the sight tracks the target. n This torque is proportional to the magnitude of the displacement between the gyroscope and the support and upon the strength of the coupling means between the gyroscope and the support; in otherv words, it is dependent upon the speed of the target and the strength of the coupling means. As Johnson points out, the strength of the coupling means is controlled in accordance with the time of flight of the projectile to the target, and therefore, the line of sight, controlled by the position of the gyroscope relative to the support, is deflected with reference to the gun by an amount which` is dependent upon the targets velocity and the time of flight of the projectile. Conscquently, the observer, by his very act of keeping the line of sight on the target, necessarily advances the gun with reference to the line of sight through an angle equal to the angle of lag of the gyroscope, and this angular advance is the correct lead for the gun -as req'uired by the targets velocity.

The present invention utilizes the foregoing elements of the Johnson sighting mechanism. But in addition it introduces further corrections and refinements in the system, and more `speciiically, :it `includes lan improved combination of elements forshifting a shiftable element of the coupling means between the gyroscope and its tion of the gyroscope and hence the direction of the line of sight so as vto introduce ballistic corrections for the elfect of wind blowing the projectile back along the line of llight of the ship and the effect on the dropping of the projectile due to gravity while the projectile is traveling the range distance of the target. More specifically, a resolving bar is connected to the shiftable coupling element to control its position, and the position of the bar with reference tothe line of re of the gun is controlled in accordance with the altitude and air speed of own ship, the elfect of gravity on the projectile, and the positions of the gun in azimuth and elevation; the position of the coupling element is controlled so that the eiects of wind and gravity are introduced in order to correct the position of the 'gun With reference to the `line of sight.

For a more complete understanding of the invention, reference should be had to the accompanying drawings in which Fig. l is a fragmentary .perspective view, largely in section, illustrating certain `elements of the sighting mechanism of this invention; Fig. 2 likewise is a fragmentary perspective view, but illustrating certain other elements of this sighting mechanism, parts also lbeing shown in section; Fig. 3 is a perspective view illustrating this sighting mechanism as applied to control :machine guns mounted in the turret of an airplane; and Fig. 4 is a diagrammatic representation illustrating a control system for controlling an element yof the coupling used in the sighting mechanism of this invention.

Referring now to the drawings, this invention has been shown in one form as applied `to Vthe control of machine guns 10 and 11 (Fig. 3) arranged in parallel relation, as shown, and supported 'to move in elevation `on a common axis in a suitable turret. The turret, as shown, has a rotatable ring 12 on which the guns are mounted by means of supporting arms 13, which-are shown diagrammatically in Fig. 3, and one of which is shown in detail in Fig. 1. These arms are attached to the ring 12 and pivotally support the :guns by shafts 14 for movement in elevation on the common axis. The `ring 12 is rotatably mounted in a Xed turret ring 15 by 'means of bearings 16 so that the guns can `be swung in azimuth `about a vertical axis. The` bearings 16 are shown diagrammatically in Fig. 3, and in detail in Fig. l. It will be understood that the gunner and observer will sit in the turret and will grasp the handles 10a and 11a of the guns to move the guns and turret in azimuth, and to elevate the guns with reference `to the turret in orde to -direct the guns generally toward the target. vAs willbe seen later the guns are not pointed directly at the present position of the target, but are advanced with reference to the line of sight to the target in order to compensate for'certain factors such as windage, gravity and velocity of the target so that a hit may be scored. The movable turret is provided with a seat 16izfor the observer and gunner. The major portion of the `elements of the sighting mechanism are mounted inra casing 17. This casing has a supporting arm 18 on one side (Fig. 3) which is `pivotally mounted on the adjacent turret arm 13 by fmeans of a shaft 19, and o'n its other side is provided 'with a bearing Ztl (Fig. l) which is mountedon a race on a 'xed part 20a that is secured to the adjacent turret arm 13. The arm 18 is extended beyond its shaft 19, as shown in Fig. 3, and the end of this extension is connected to the gun 10 by a link 21. The opposite side of the casing ris connected to the gun 11 by a similar link 22 so `that as the gun moves in elevation the-casing is moved with it and on an axis parallel to the .guns elevation axis.

The casing 17 has a sighting section 23 at one-side, as shown in Fig. 3. The rear wall of this casing section is provided with a pair of sight openings 24 back of which the observer sits in the seat 16a and through which 2,859,526 I v A.

he views the target. These openings are covered by clear glass. 'Ille entire front of the section 23 is open and is covered by a large piece of clear glass.

Mounted within the sight section 23 opposite the righthand sight opening, as viewed in Fig. 3, is a transparent re'ector member 25 (Fig. 2) which may be formed of clear glass. VIt will be observed, therefore, that the observer may use both his left and right eyes-indicated 26 and 27 in Fig. 2-in order to view the target.

The reflector 25 is mounted in a frame 28. The frame 28 is mounted for movement in azimuth on the two arms 29 of a gimbal ring 30 by means of shafts 31, the two arms extending through the casing section 23 into the casing proper where the ring 30 is located. i

The movement of the transparent reflector 25 in `lateral deection as well as in vertical deflection is 'controlled by means of a gyroscope 32 mounted in the casing 17. The gyroscope is driven by a motor 32a which is mounted in the ring 30 for motion in lateral deflection by means of shafts 33. The ring 30 is mounted for movement on an axis at right angles to the axis of movement of the gyroscope in the ring 30, and for this purpose it is provided with shafts 34 journaled in bearings 35 fixed in the casing 17. The frame 28 of the reflector is connected to the gyroscope motor by a link 36 pivotally connected to the movable frame 28 by a shaft 37 and to the motor by a shaft 38. The connection between the gyroscope and frame 28 is such that the reflector 25 is moved in lateral dellection through approximately onehalf of the angle of movement of the gyroscope 32 in lateral deflection. In the specific embodiment of the invention illustrated in the drawings, the gyroscope 32 has a motion on its shafts 33 of plus or minus 14 from its zero position, that is, ithas a total motion of 28, while the reflector 28 has a motion on its shafts of plus or minus 7 from its zero position, or has a total motion of 14.

Close to the position and also at both 14 positions (plus and minus) of the gyroscope, the error in move` ment of the reflector from exactly one-half of the angle of` movement of the gyroscope is practically zero. The error in the movement of the reflector increases Yslightly fromv this zero error to a maximum of .019 at about 7 displacement of the gyroscope from its 0 and 14 positions. This is a positive error; in other words,'at the positions of maximum error the reflector is moved .019 too much. The amount of error, of course, depends upon the ,constants selected in the linkage between the gyroscope and the reflector. In the specific application where the constants are such that the maximum error' is only .019 the effects thereof `are negligible for all practical purposes. The reflector, of course, is'moved on a vertical deflection axis-an axis through the shafts 34- bythe arms 29 which are connected to the gimbal 'ring 30. The parts are so constructed and arranged `that the line of sight through the reflector'25 always is parallel to the spin axis of the gyroscope which, ofcourse, is the aJzris of the motor shaft that operates the gyroscope' wheel The transparent reflector is one element of an optical system for establishing a line of sight by creating a luminous imagein the field of view of the observer, and also for determining the range of the targetV by framing the target in the luminous image; this image preferably will be in the form of a circle of eircuinferentiallyV spaced luminous dots, the diameter of which is variable. I prefer to use the optical system described and claimed in: my copending application, Serial No. 443,031, tiled May 15, 1942, now Patent No. 2,406,828 and assigned to the sameassignee as the present invention. This system `comprises a source of light 39, shown as an electric incandescent lamp; a condenser lens 40; a reticle range nder unit 41; reflecting mirrors 42 and 43; a collimating lens 44 for creating collimated light; and the reflecting glass 25,'al1 mounted within theV casing 17. Here the collimating lens 44 is positioned so that the vcollimated light axis circle of dots and when adjustedto frame a targetofl is coincident with'the axis of rotation of the ring 30 in y order that the line of sight shall always be parallel the gyroscopes spin axis.

As pointed out in detail in my afore-mentioned co' pending application, the optical system generates in the field of view of the observer a luminous circle formed4 of a series of circumferentially spaced dots of light.l Also as there pointed out, the range finder has four units 41a, 41b, 41e and 41d, calibrated to different known target sizes; and each set has a pair of functional dislrsf,VY 45 which are rotated in opposite directions with refs.'` erence to a xed reticle (not shown) and thereby pro-v vide a series of intersecting openings arranged in a circle and through which light can pass from the bulb 39 in order to form the circle of circumferentially spaced dots'. f In this way, the luminous circular image in the eld of-V view of the observer is generated. When the disks are.. rotated relative to each other they vary the size of the known size they determine the targets range. .Y The four sets of cooperating disks 41a-41d areY rotatable into functional relationship with the fixed reticle in order 'to bring the proper set into operation for a particular target by means of a shaft 46 controlled by a knob 47- located outside of the casing 17 And the particular set of disks j; that is in control are rotated relatively to each otherto vary the diameter of the range finding luminous circle, and thereby determine the targets range, by meansoffV a driving shaft 48. This shaft is connected by -bevel gears 49 to a driving shaft 50 which in turn isl connected,r to a driving shaft 51 by means of bevel gears 52. The shafts 48, 50 and 51 are located in the sight casing 17K.' The shaft 51, in turn, is driven by a flexible shaft 53 out` side of the sight casing and which is operated by afoot pedal54 through a shaft 55, rack segment 56,- pinion V57; shaft 58 and bevel gears 59. The foot pedal is outsider of the casing and is located where it canA be operated'con'- j; veniently by the foot of the observer as he sits'in theY seat 16a. A fixed stop pin 59a enters a circ-le 59b inthe rack segment in order to limit the up and 'down-move, -l ment of the pedal 54. The pedal is biased'upwardly by Y a suitable spring (not shown), The position of the gyroscope and hence-,that offthe Y Y line of sight is controlled by means of an 'erecting elee tromagnet 60 located within the casing 17. This Imagnet has a winding 61 located about a central pole piece`62 and also is provided with outer pole pieces 63. magnet seats on a spherical bearing'seat v64; it is sup-U ported by a resolver rod 65, and is held against thebearfV ing seat by means of a plurality of spaced guides 65a. The seat 64 is mounted on a xed part 66 attached'to the casing 17. And the spherical seat is so arranged that Y irrespective of the position of the magnet on the seat, the i position of the magnetic axis-which here is the centralV axis of the central pole 61-always intersectsthe point of suspension of the gyroscope, that is, always intersects point of intersection of the two axes of 'movement vof the gyroscope. The lengths and shapes of the central and outer p ole pieces 62 and 63 of the magnet 60 are such thatltheilj4 outer ends lie on a spherical surface having a centerV atV the center of suspension of the gyroscope.` Q

A ball and socket joint 67 connects the rod 6 5, vvitl1 v the magnet 60. r.

In the magnetic eldgenerated by the magnet 60 t, eddy-current disk 69 mounted on the gyroscope for rota' tion on .an axis coincident with the spin axis ofthe scope. The eddy-current disk'is rotatedA by the gyroscope motor 32a; and it comprises a soft iron disk over which is spun an electrically conducting sheet. The disk has` an outer curved surface approximately in the form ofgy segment of a sphere which has Vits center in the centervv of suspension of the gyroscope 32. Y The eddy-current disk 69 and themagnet lvllconstitlfto a coupling between the gyroscope 32 and the casing 17.` l

This .coupling applies. a torquetothe gyroseope p32myvhih,

tendsto` process vit i into alignment j wjthhemaxis o; the magnet. y.It kwill .be understood thatll .the .QPQIHQQ Of this coupling, .when the eddy-current ,diskm69. `is rotated in the magneticeldset up by..the magnet'. andthe axis of the.gyroscopeis` alignedwiththe axis of', the magnet 4no eddy currents `are .inducedlin theidisk, whihwill tend to precess 4.the gyroscope. YHowever, it the Aaxismvof` the magnet is energized, the` magnetic attraction fQr-thejdisk holds the magnet rmlyon its ,SphericaLseat 64,

Here it is ,to be observed that ,whenthehguns and 11 are moved in space in order to carrytheight` casing 17 and hence the transparent reectonZS with them to i cause the line of sight tobear upon and track atarget, the gyroscope will lag behind the casing by amountdependent upon the speed of. the targetuand alsoupon the amount ofcurrent exciting the magnet 60,. And `aswill be pointed out in greater detail hereinafter ,in aldetailed discussion of the operation `ojfthe ,sighting mechanism, this Current is controlled in accordancewiththe timevof flight of the projectile to thetargetso that the gyroscopes lag is ameasure Iof the guns lead angle required by the speed of the target.

In addition, the position corrections in the line of tire of .the gunszwhichcorrectionsfare` for wind, as it blows the projectiles back along the line of flight of the airship which carries the-guns,` and also for gravity which, of course, pullsthe projectilesr downwardly.. The means per se for introducing the Ihallistic corrections does not .constitute a partgof this invention, but is the inventionof VJohn R. MooreLand is `described and claimed in hisA copending application, Serial No.` 492,518, tiled4 June 28, 1943, and whichapplication is assigned to the same assignee as this application.- The ballistic corrections are introduced byA shifting the positiony of the resolver bar. 65` to shift the magnet by the proper amount. i

The resolver bar 65 is formed two 72 and73 in telescopic relation, as shownin Fig.` 1. ,The outer part 73` is connected at `one end to the magnet through` the ball joint 67 and its other end receives` the .other,part 7,2. Also the outer part 73 is connected to an adjustable` nut 74 forming a universal fulcrum `for ithe rod 65` by a uni, versal connection comprisinga-collar75 `slidavbleon the outer part and having opposed shafts 76 mounted inthe two arms of a U-shaped bracket 77.5 The nexus of this bracket is pivoted to the nut`74 by a bolt 78. Thefnt 74 isrthreaded on a worm which is mounted in the casing 17 to rotate on a iixed` axis parallelwith the guns axes, that is, With their line ofre. Then'utl isprevented `from rotating with the wormby a guide 79a in which a roller 79b moves; thisfroller is attached to the nut by a rod 79C, as shown. .They/,crm 79 is driven by bevel gears 80 from Vthe shaft `51.and 4therefore, the fulcrum for the resolver rod 65 -is adjusted axiallyalong the length ofthe rod in'` accordancelwith rangeforY a purpose to be brought out in thedetailed description of operation of the sight. The range worm 794 also sets two rheostats S1 and 82 in accordance `with rangefona purpose also to be describedwherenafter. ,Thewworm `of the magnet 60` issliiftedy on its spherical bearing 64 in orderto introduceballistic` ves the rheostats through a spur gear 83 meshing with spur gears 8 4 andhSAS which s et the rheostats,

The @sist 60, thatgis, the outer end of theiniierV part 72 of the rod,

carries a `ball (Fig. l) and this ball is mountedin a socket 8 7 formedas the segment of a sphere. It Willbe observed thatthesocket 87 supports the sphere 86 so that theaxis ofthejresolver rod lies below the axis of elevation otgthelsighting device. This is for the purpose-` of compensating for gravity, as will be explained in detail later in the descriptio mechanism.

rut-seeker 87 is' secured to the head ss of a pin e9.'

The 'pin 89 is mounted for rotation in post 90. The post pin A89 is rotatably mounted. ASecuret'l' to the upper end ofthe post 90 isa `plate 91 in the form of a crank'arm and the pin"89also extends lthrough an opening in the outer end of this arm so that the head 88 of the pin* restsgon .they plata The upper end of the post 90 extends through a disk 92, which I will `refer to as *the azimuth disk, this diskV being provided with an; elongated diametral slot 94 through' which the post is directed, and the side edges of which closely tit the adjacent sides ofthe post. As shownhthe plate 9 1 rests upon the upper surface of the disk `92. l

The disk 92 has a depending skirt 95 having an inwardly oiset bottom section around which ball bearings 96 are mounted, and which rotatably support the disk in a bearingseat 97; this seat is mounted in the casing 17,

but it is xed to the element 20a which is outside of the casingand which is connected to the turret arm 13 to move in azimuth with it. The seat 97, therefore, does not` move in elevation With the sight casing 17.

The lower parts of the post 90 are guided by a block 9Sunder,the disk 92; this block has a slot 99 registering with the VVslot 94 and receiving and guiding the post 90;

the block 98 is rigidly secured to the azimuth disk 92 and isq rotated ,with` it. Under the block 98 and secured to it is a circular disk-like plate 100 which projects under the bearings 96, as shown, and which has a recess 101 for A receiving the post 90.

Depending from the post 90 and in axial alignment with itis :a cylindrical column 102; and mounted on this column and abutting the bottom of the post'and also the bottom surface of the disk 100 is a plate 103; and fastened belowthe plate 103 is a rack 104 which is suspended from the block 98, and which guides the plate, as shown. A spurv gearY 105 is mounted on the column 102 for free i attached to the spur gear 105 and so that when4 it rotates it rotates thejgear Withit.

It will be observed that when the cylinder 106 is turned it Will rotate the spur gear 105 on the rack 104, and hence, will move theV Whole assembly of parts-that is, the sphericalsocket 87, the ball 86, the plate 91 and pin 89,*the post v90,the plate 103, thecolumn 102, the cylinder 106, and the spring 107-allacross the diameter of the` azimuth disk 92. This in eiect adjusts the position of the axis of movement ofthe ball 86 on the pin 89 radially with reference to the center ofthe disk 92, the telescopic construction of the rod 65, of course, permitting this adjustment. I i

y' Fl1e-cylinder'106 is locked in its adjusted positions by j irma.; ...a

e resolver rod 65 opposite the lmagnet i nV of the operation of the sighting sight'V is mounted.

depending Yfrom it. Y This pin is receivable in any one of a number of holes 1-11 in the top wall of the cylinder and corresponding to a series of controlling positions of the cylinder and hence to a series of radially adjusted positions of the ballV 86 across the disk 92. To adjust the cylinder and hence the ball, it is only necessary to pull the cylinder down to release it from the pin, turn it to the new` position, and release it. so that the pin again locks the cylinder.

The cylinder 106 is adjustable in accordance with the altitude and air speed of own ship. For this purpose it coacts with an altitude scale 111a which is graduated in thousands of'yards altitude. The altitude scale is carried by thef'plate 103. Inscribed on the outer surface of the cylinder are a seris'of Iies'111b'for'ming an air VspeedV scale, .which is adapted to register with the graduations on Vthe altitude scale. In order to set the device for a given altitudefand air speed, the proper air speed line 111b is moved until it intersects the proper altitude line on the altitudescale. This sets the 'radial position of the ball 86' in terms of altitude and air speed, and hence, adjusts the rod '65 in vthese terms.

A pin 112 tixed to the lixed support 97 is directed through the spherical socket 87, as shown, and tends to align the'socket with the resolver rod 65, irrespective of the adjustments given the socket with relation to the azim'uth disk 92.

The position of the azimuth disk 92 with reference to its support 97 that moves with the turret in azimuth is controlled by Va driving connection with the xed turret ring ;VK this driving connection comprises a spur gear 113 formed on the periphery of the azimuth disk 92, and which meshes with a spur gear 114 mounted upon a driving shaft115. The driving shaft 115 is driven by means of` a worm wheel 116 secured to it and which meshes with a driving worm 117 operated by a shaft 118. The shaft 118 is driven by bevel gears 119. The gear 114,'the shaft 115, the wheel 116, the worm gear 117 and the shaft 118 are mounted in the casing 17 of the sight. The bevel gearing119 is secured by means of a flexible driving shaft 120 to a driving shaft 121 outside ofthe casing 17 and which is driven from the fixed turret ring 15 by means of a spur gear 122 that meshes with a rack 123 formed on the turret ring. The drive is constructed and arranged so that when the sight is movedv turret and in'ja reverse Ysense so that it remains fixed with reference tothe fixed` turret ring 15; in other words, it remainsf'iixed with reference to the ship upon which the The 'driving shaft 121 also functions to set :a suitable rheostat 124 for a purpose which will be described in detail when the operation ofthe sighting mechanism is described.l The shaft 121 is connected to the setting member of the rheostat 124 by means'of a'worm 125 xed to the shaft and meshing with a worm wheel 126 secured to the setting member of the rheostat.

The gyroscope 32 which is controlled by the magnetic coupling described above is subject to violent nutation movements under certain `operating conditions. To obviate this effect, a nutation damper is provided on the end of the gyroscope assembly opposite the eddy-current disk 71. This `damper comprises an annular weighted ring 128 (Fig. 2) which is pivoted on an inner liexible ring 1,29 by means of pivot pins 130 located on the opposite ends of a diameter, as shown. The ring 129v is pivoted to the motor 32a by means ,of pins 131 also located at the opposite ends of the diameter, but which is at right angles to the axis of movement of the ring 128 with reference to the vring 129. The pins 130 and 131 are in the form The telescopic construction of theV is determined bythe network disclosed in Fig. 4.Y Thef motions of-,thegyroscope produce relative'motions'bo- 'filed May 17, 1943,Y and which application is assigned;

of 'screws and they are adjusted so thatl a predetermined resistanceto mbtionis setup between the two. rings and between the inner ring and the motor casing. Nutationgl tween the two rings and between the inner ring.129 and..l the motor casing. The frictional forces produced by these movements cause the nutation to b e damped. Suit#- able circumferentially spaced stopsi132 are provided on the motor 32a toY engage the weighted ring 128 to limit its movement, the stops providingsome impact damping,v Preferably, these stops will be made of a suitable resilient materiahsuch as lsponge rubber. Y The g foregoing nutation Adamper is Adescribed claimed in my divisional application, Serial No. 487,309, Y

the assignee of the present application.

VAspointed out previously, the magnetic effect ofA the magnet 60 is controlled'in accordance with the time of flight of the projectile; this'is accomplished by controlling the amount ofcurrent that flows through` the magnet winding 61. The control system for the winding 6` is shown diagrammatically in Fig. 4. This system ,com-S prises the two resistances 81 and 82, which are adjusted.;Y inl Vaccordance with range, as pointed out previously;'4 the rheostat 124 which is operated in accordance with@` the azimuth movement of the turret and the sighting; mechanism mounted within it, since it is drivenY from the iixed turret ring 123, as pointed out previously; a rheostatv 133 `adjusted in accordance with the altitu'def,l and air speed of own ship; a rheostat 134 adjustedfin;- accordance with the altitude of own ship; and a ballast. lamp 135. The rheostats 133 and 134 and the, ballast lamp'135 are mounted in a controlzbox 136 (Fig. 3,); they two range rheostats 81 and 82 are mounted in the sight casing 17, while the azimuth rheostat 124 is located-, where it may be conveniently driven from the shaft 121,1 as shown in Fig. 3. The altitude and air speed rheostat 133 is set by a manual control knob 137, while the al tude rheostat 134 is set by a manual control knob 13B; The azimuth rheostat 124, as has been pointed out, "is mechanically controlled from the fixed turret ring 15, as thesight moves in azimuth, while the other twofrh stats 81 -and-82 are automatically controlled in accordance' with the setting of the range nder. Y'

In operation: It will be understood that the observer will look through the transparent reflector 25 at the target. He willthen bring the proper set of reticle disks, required by' the particular target, into operation by the` knob47. 'Ihe circle of luminous dots created bythe optical Vrange finding system willr be observed in his eld of view. v He will move the guns in azimuth and eleva tion in vorder tobring this luminous image onto the taff; get, and hevwill move the turret and guns continuously` to keep it upon the target. Also he will shift the foot.; pedal 54 inorder to frame the target by the reticle imago` and therebyfdetermine the targets range.l As he tracks the target, the sight casing 17, of course, moves along with the guns, b ut the gyroscope 32 and the parallel line of sight controlled by the gyroscope lag lbehind the cas ing, and necessarily, therefore, lag behind the line'fof tire of the guns. The angular velocity of the target, of course, is measured by the velocity of 'the sight in caus ing the lineof sight to track the target; and the time of ilightis introduced by controlling the current of the magg net v60 .so that the displacement of the gyroscope, and hence thatrof the line of sight with reference to the guns,y line of tire is proportional `to the product of the time of ilight times the angular velocity of the target, and con?` sequently, is the correctv leadV angle that is made neces? sary byv the -velocity of the target. Y

' The control of the magnets exciting current and hence the time of flight correction, as pointed out previously;

ballast lamp of this network compensates for changes.,

inthe ship voltage so that the output is approximately constant current.

The setting of the resistance 133 in terms of altitude and air speed, and the settings in azimuth of resistance 124, connected in series with resistance 133, compensate for the time of flight for variations for dierent azimuth angles caused by the wind blowing against the projectile. All of this is because the effect of wind as it affects time of flight varies with the speed of own ship; and it also varies with altitude, because the characteristics of the fairat higher altitudes have less resisting effects on the projectile; and the azimuth rheostat settingy is necessary because the resistance of the wind to the flight of the p rojetile varies with the relative directionl of the wind, and hence, depends upon the position of the guns in azimuth.

While similar corrections may be made for the position of the guns in elevation, in the particular apparatus disclosed, this isnotnecessary because high elevation angles are not encountered.

`The altitude rheostat 134 in a circuit in parallel with the circuit of rheostats 133 and 124 is set to altitude to correct the time of flight for the variations in the resistance to flight of the projectile due to variations in air density.

The corrected time functionfeeds a constant resistance network consisting o f the rangerheostats 81 and 8,2v which introduce the range function from the. range pedal 54. The resistance 81 is parallel to the magnet winding 61 and the resistance 82 is in series with it. The rheostats 81; and 82 have resistances which Vary with rotation so that they vcompute the correct time of flight from that function of range required by range worm screw `79.

. Aslafresultof the foregoing control, the flux generated by themagnet 60 is proportional to the current supplied tothe. magnet winding 61 and is inversely proportional to the square root of time of flight.

It will be observed, therefore, that if the observer moves the guns 1() and 11 inrazimuth and elevation to cause the luminous reticle image to follow the target and if he has` operated the foot pedal 54 to measure range by framing the target by the reticle image he will cause the gyroscope toV lag by the correct lead angle, as required by the targets` velocity. And in keeping the line of sight on the target he will automatically offset the guns byfthecorrectlead angle.

Butthe position of the magnet 60 is changed to control the positionA of the gyroscope, and hence that of the line of si'ght withV reference to the guns line of fire in order to introduce the ballistic corrections for wind and gravity.

The effect of wind on the trajectory of the projectile depends upon the air speed of own ship, its altitude, .and the` position of the guns in elevation and azimuth.

With reference to the position of the guns: If the guns point straight forward or straight backward in the line offlight of own ship thewind does not deflect the projectile at allin the azimuth sense. But at all intermediate. positions it does do so, the maximum deflection taking place when the guns` are approximately at right angles` to theV line of flight ofown ship. In elevation, the maximum effect of wind on the projectile takes place when` the guns lare approximately at right angles to the lineofflight-of own ship and decrease as the` guns move toward straight ahead` or straight rearward positions in the line of flight, becoming a minimum when thel guns are` directed straight forwardly or rearwardly in the line of ight. As to air speed, the deilecting effects on the projectiles trajectory for any given setting of the guns, ofcourse, increaseswith increases-in air speed, and vice versa. Also the deflecting effects of the air` decrease with altitude, All of these factors are taken into consideration when adjusting the position of the` magnet 60 by theresolyer rod 65.` And, ofcourse, the resultant effects ofr allot these factors depends upon the lengthy of time the projectile is in the air, that is, they depend on the '10 rangeof the target, and-this correction also is introduced by adjusting the Vposition ofthe rod 65.

The angular position of the rod 65 is adjusted about its universal fulcrum on nut 74 in accordance with altitude and air speed by adjusting the position ofv the socket 87 radiallyl with reference to the azimuth disk 92; and` this is accomplished by properly setting the air speed scale lllb on the cylinder 106 against the altitude scale 111a. The position of the guns in azimuth and elevation, of course, move the rod 65 about its-fulcrum nut 74 since the azimuth disk 92 remains fixed with reference to own ship while the guns move the rod 65 with them in azimuth and elevation with reference to own ship. The setting of the air speed and altitude to adjust the radial position of the ball 86, and the adjustment of the rod 65 by the azimuth and elevation positions taken by the guns at any time shifts the rod 65 on its fulcrum or nut '74, which, of course, shifts the magnet 60 and hence, the gyroscope and line of sight, the direction of the shift depending, of course, upon the position of the guns, and alsoupon the altitude and air speed setting.

Ina similar way gravity is introduced: But as it is of constant value it is permanently set in by positioning the ball 86 below the sights elevation axis, as pointed out previously. This, of course, causes the -bar 65 to slope upwardly about its, fulcrum which causes the gyroscope to depress the line of sight. To restore it, the guns must be elevated and the dropping of the projectile is compensated for.

But these factors of wind and gravity must be corrected for the length of time that the projectile is in the air, that is, in accordance with the range of the target. This factoris introduced by adjusting the fulcrum on the nut 74 by the foot pedal 54 in the mannerpreviously described' This setting in effect multiplies the wind and gravity inputs-introduced by moving the ball 86 radially by 109, and lowering it below the elevation axis by the xed gravity distance-by the range input. At shorter ranges the fulcrum 74 is closer to the magnet so that the magnet displacement is small, whereas at the longer ranges, the fulcrum is moved toward the azimuth disk 92 so that the magnet displacement is greater.

Therefore, superimposed upon the lead angle given the guns, as required by the velocity of the target and time of Hight of the projectile, are the corrections in the angular position of the guns with reference to the line of sight required by wind and gravity as they affect the projectiles trajectory to the target.

In one particular set of battle conditions the relative positions of the axes of the guns, the slide rod, the magnetic axis, and the spin axis of the gyroscope are illustrated in Figs. l and 2 taken together. The various axes are appropriately labeled.

Summing up the operation briey: The reticle lamp 39 is energized; the altituderheostat knob 13:8 is set at the position corresponding to the altitude of the ship; the altitude and air speed rheostat knob 137 is set at the indicated altitude and air speed; andthe ballistic cornputer altitude and air speed setting is made by the knob 109 in accordance with the altitude and air speed requirements.

When a target (enemy aircraft of known size) is sighted, the target span knob 47 is turned to a position corresponding to the wing span of the target. After the correct target span setting has been selected, the target is ringed by the reticle dots by shifting the guns in elevation and the turret in azimuth as required by the movements of the target. As the target range varies, the foot pedal 54 should be depressed or allowed to swing. up so thatthre target is kept just inside the luminous ring of dots. As the sighting mechanism, is immovably fixed to the guns and the guns in turn are linked to the turret drive, it follows that after proper ballistic corrections have been setas noted above all that remains f or the observer and gunner to do is to follow the target by "1'1 meansof the turret and the guns. Preferably, the'guns will be provided with tiring triggers so that they may be fired `by the observer asghe tracks the 'target."-- v i t What I claim as new and desire to secure by Letters Patent of the United States is: l ,1. Gun sighting mechanis-m comprising means for establishing a line of sight, a gyroscope connected to said means so that said line of sight is maintained in known angular relation to the gyroscopes spin axis, a member adapted to be moved with the gun, a coupling between said member and said gyroscope having a pair of coacting elements one on said gyroscope and the other on said member, said elements applying to said gyroscope a precessing torque to cause it to tend to follow said member as it is moved so as to cause said line of sight to track Ya target, means forcontrolling said torque so that the position of said gyroscope with reference to said member measures the lead angle of the gun required by the speed of thev target, and means for shifting one of the elements of said coupling means so as to displace said gyroscope andthe line of sight controlled thereby in accordance with the eie'cts of wind and gravity on the iiightof the projectile from the gun to a target. y -2.Sigl1ting mechanism for a gun comprising sighting means Afor establishing a line of` sight, a gyroscope, a

. mount for said sighting means and gyroscope movable in train and elevation with said gun in order to cause said line of sight to'track a target, means interconnecting said gyroscope with said sighting means maintaining said line of sight in known angular relation to the spin axis of said gyroscope,`coupling means between said mount and gyroscope having a pair of coacting elements one on said gyroscope and the other on said mount, said elements applying a torque to said gyroscope in order to cause it to precess to tend to follow -said mount as the mount moves in keeping said line of sight on the target, means controlling t'he `coupling effect of said coupling means in accordance `with the time of ight of a projectile from the gun to a target, and means for shifting the position of one of the elements of said coupling means in order to displace said gyroscope and the line of sight controlled by it in order to compensate for the eiects of wind and gravity on the trajectory of said projectile.

, 3. Sighting mechanism for a gun mounted on aircraft comprising sighting means for establishing a line of sight, a gyroscope, a mount for said sighting means and gyroscopehmovable in train and elevation with said gun in order'to cause Said 'line of sight to track a target, connection means between said gyroscope and said sighting means'y maintaining said line of sight in known angular relation to the spin axis of said gyroscope, relatively movable coupling elements on said mount and gyroscope respectively applying a torque to said ygyroscope in order tocause it to precess to tend to follow said mount as the mount moves in keeping said line of sight on the target, means controlling said coupling elements to control said torque in accordance with the time of ilight of a projectile from the gun to the target, a resolver rod on said mount and connected to one of ysaid coupling elements forcontrolling its position in accordance with the position of said rod, and means for adjusting the position of said rod relative to said mount in accordance with the position of said gun in azimuth and elevation, the altitude and air speed of said aircraft, the effects of gravity on said projectile, and the range of said target all in order to adjust the position of said gyroscope and the Iline of sight controlled by it relative to said gun to compensate for the actions of 'wind and Igravity on the flight of said projectile.

v4. Sighting mechanism for a gun mounted on aircraft comprising sighting means for establishing a line of sight, a'gyroscope, a mount for said sighting means and gyroscope movable Ain train and elevation with said gun in order to cause said line of sight to track a target,'con nection means between' said gyroscope and said sighting 12 l Y means -maintaining said line of sight in knownangullijfL relation to the spin axis of said gyroscope, couplingmeans` having Ya pair of coacting coupling elements on izsaid mount and'gyroscope respectively applying a torquegtg said gyroscope in order to cause it to precess totQnd/.IO follow Said mount'as the mount moves in keeping line `of sight on the target, means controlling the coupling'V elect of said coupling means in accordance with the time 0f flight of a projectile to the target, a resolver rodV on, said mount and having one end connected to oneclcment of said coupling means to control its position with refejg ence to the other element and therebythe position said gyroscope, a universal fulcrum for said rod,rr reaij| for adjusting the position of -said fulcrum along Itho ff Q length of said rod in accordance with the rangeof saldi? target, means controlling the position of the other end; said rod in accordance with the positions of said gun azimuth, the altitude and air speed of said aircrafnd;v also of gravity so that the position of said gyroscope` the direction of said line of sight is deected with refer; ence to the line of lire of said gun in order to compensate. for the effects ofwind and gravity on the ilight of projectile.

5. Sighting mechanism for a gun mounted on aircraft:V `comprising a lsight for establishing a line of sight togl.. target, a support for said sight, a gimbal Yring on saidy-j support mounted for rotation on an axis, a gyroscope said ring mounted for movement on an axis at right angles to said axis of movement of said ring, connection`vv `Y means between said gyroscope and sight so that the tion of `said line of sight is maintained in known angulg relation to the gyroscopes spin axis, said support ,bef movable in train and elevation with said gun sons keep the line of sight on a target, an electromagne coupling having relatively movable elements between w, support and said gyroscope for applying `to said gyrs'copo a precessing torque to cau-se it to'ten'd to follow said fsupg j port, means controlling the magnetic coupling eiect-off-Vi said coupling in accordance with the time of night `of;A projectile to said target, a resolver rod having one 'end connected to one element of said coupling means to trol its position with reference to another element thereof,kk if a universal fulcrum for said rod slidable with referentirv to the rod, means for adjusting the position of said: crum along the length of said rod in accordance' the range of said target, and holding means for theothexf end Of said rod adjustable inN accordance with thef'po-ei; tion of said gun in azimuth,the altitudeand air Speedo! said aircraft, and gravity so Vthat said line Vof sight is ected in order to Icompensate for the effects of windk p gravity on the flight of said projectile.

6. Sighting mechanism for a gun comprising sightingVV means for establishing a line of sight, a gyroscopefj mount for said sighting means and gyroscope movablefin train and elevation with said gun in order to cause line of sight to track a target, connection means between said gyroscope and said sighting means maintaining said" f line of sight in known angular relation to thespin Y of said gyroscope, connection means between said maar? I and gyroscope for causing a displacement between sai gyroscope and said mount which is a function of angular velocity of said line of sight and the time Vof ght of a projectile to said target, and `additional mea'iig acting on said last named connection means in order displace said gyroscope with reference to said support` by an amount which is a function of the azimuth and elevation positions of said gun, functionsof the altitu and air speed of, said aircraft and gravity multiplied by function of the range of said target, all to compensate-f the eiects of wind and gravity on the ilight of a projectile from said gun to the target. Y 7., AV gun sighting mechanism for a gun mountedn aircraft comprising sighting means for establishing a of sight, a gyroscope, a movable support for said sigh# ing means and gyroscope, the gyroscope being motilit@`V on said support for freedom ofmovement about a center of suspension, means connecting` said` gyropscope. toV said sighting means so that said. line ofsight is maintained in known angular. relationY tothe gyroscopes spin axis and so that said line of sight in tracking a target is Controlled both by themovement of said support and the movement of said gyroscope with reference tosaidnsupport, an eddycurrent disk mounted on said gyroscope, means for rotating said eddy-current disk, a magnet for creating a magnetic eld in which said eddy-current disk rotates7 a spherical bearing seat on said support mounting said magnet so that irrespective of the position of the magnet on said bearing seat its magnetic axis intersects said center of suspension of said gyroscope, means for controlling the energization of said magnet in accordance with the time of flight of a projectle from the gun to a target, and means for adjusting the position of said magnet on said bearing seat in order to compensate the direction of the line of sight for the effects of Wind and gravity on the flight of said projectile.

8. A gun sighting mechanism for a gun mounted on aircraft comprising sighting means for establishing a line of sight, a gyroscope, a support for said sighting means and gyroscope movable with said gun, the gyroscope being mounted on said support for freedom of movement about a center of suspension, means connecting said gyroscope to said sighting means so that said line of sight is maintained in known angular relation to the spin axis of said gyroscope and said line of sight in tracking a target is controlled both by the movement of said support and the movement of said gyroscope with reference to said support, an eddy-current disk mounted on said gyroscope, means for rotating said eddy-current disk, a magnet for creating a magnetic eld in which said eddycurrent disk rotates,v a spherical bearing seat on said support mounting said magnet so that irrespective of the position of the magnet on said bearing seat its magnetic axis intersects said center of suspension of said gyroscope, means for controlling the energization of said magnet in accordance with the time of flight of a projectile from the gun to a target, a resolver rod having one of its ends connected to said magnet to adjust its position on said 'bearing seat, a universal fulcrum for said resolver rod slidable with reference to said rod, means for adjusting the position of said fulcrum along the length of said rod in accordance with the range of said target, and means for adjusting the position of the other end of said rod along a fixed axis in the azimuth plane in accordance with the altitude and air speed of said aircraft, and further positioning said other end with relation to the axis of elevation of the gun in accordance with the effect of gravity so that the rod adjusts the position of the magnet on said bearing seat in order to control the line of sight to compensate for the effects of wind and gravity on the line of flight of said projectile.

9. A gun sighting mechanism for a gun mounted on aircraft comprising a movable support adapted to move with the gun, a target sight including an optical system xed on said support but having a movable sighting element and means for forming a reticle image in the target field of view, a gyroscope on said support mounted for freedom of movement about a predetermined suspension point, a coupling having cooperating relatively movable elements between said support and gyroscope to apply a torque to precess said gyroscope to tend to follow the movement of said support, means controlling said coupling in accordance with the time of flight of a projectile from said gun to a target, means for shifting the position of one of said coupling elements in accordance with the position of said gun, the altitude and air speed of said aircraft, the effect of gravity on a projectile tired from the gun,

`and further in accordance with the range of said target to introduce corrections for the effects of wind and gravity on the liight of the projectile from the gun to the target, and connecting means between said gyroscope and said sighting element for shiftingthe position of said sighting element relative to the gun. to detiect the optical axisfofv the` target inthe lield` of-view` of said sighting element, a

reticle in said optical system, means for forming an image of said reticle in the eld of view of said target, means for adjusting the dimensions of said reticle to frame the target so as to generate the range of the target, a gyroscope on said support mounted for universal freedom of movement about a point of suspension, means connecting said gyroscope to said transparent sighting element so that the spin axis of said gyroscope is held in fixed relation to the line of sight established by said reticle, a coupling having a pair of coacting elements on said gyroscope and said support respectively applying a torque to said gyroscope to precess it to cause its spin axis to tend to follow the movement of said support, means controlling the coupling effect of said coupling so as to control said torque in accordance with the time of flight of a projectile from said gun to said target, and which torque varies with the angle between said coupling elements, a resolver rod, means for connecting one end of said resolver rod to one of said coupling elements, a fulcrum for said resolver rod, means for adjusting the position of said fulcrum lengthwise along said resolver rod in accordance with the range of the target, and means for holding the other end of said resolver rod, means for adjusting the holding means in an azimuth plane fixed with reference to said aircraft in accordance with the altitude and air speed of said aircraft, means for positioning said holding means in a vertical plane in accordance with the gravity effect, all so that the position of said rod and that of said one coupling element .is adjusted in order to control the position of the gyroscope and thereby said line of sight to compensate for the effects of wind and gravity on the flight of the projectile.

1l. A sighting mechanism for a gun comprising a sight for establishing a line of sight, a support for said sight, a gyroscope mounted on said support having freedom of movement with reference to it about a point of suspension, means connecting said gyroscope to said sight so that the line of sight is maintained in known angular relation to the spin axis of said gyroscope, a coupling between said gyroscope and said support applying to said gyroscope a torque tending to precess it to follow the movements of said support, means for computing the rangeof a target, and means responsive to said lastnamed means for mechanically and electrically controlling the coupling effect of said coupling means.

12. Sighting mechanism for forming a reticle image in a field of View and for controlling the position of said image in said field of View comprising a reticle, a source of light for illuminating said reticle, collimating lens for collimating the image of said reticle, an optical system for projecting the image of said reticle along a predetermined direction line, a transparent reflector through which said field of view is observed, a frame supporting said reflector, means supporting said frame for relative rotative motion with reference to said reticle forming means about an axis which axis is coincident. with said direction line, a gyroscope mounted in said frame for motion on an axis at right angles to said axes, means on said frame providing for rotation of said reflector on an axis parallel to said axis of motion of said gyroscope on said frame, means connecting said gyroscope with said reector so that the position of said reector with reference to said frame is controlled by the position of said gyroscope on its axis of movement on said frame, and means controlling the position of said gyroscope to de termine the position of saidfra'me and hence of said reflector about the axis of motion of said frame, and also the position of said reector about its axis of movement on said frame.

References Cited in the le of this patent UNITED STATES PATENTS Cowles Nov. 16, 1920 Sperry Ian. 15, 1924.10

v France June 19, 1933: 

